Sealing crevices in oil wells



Patented June 10, 1952 UNITED STATES PATENT OFF-ICE.

2,600,195 SEALING. o mv cns IN on. WELLS on d 0.3 Nort ok lllefisfii w! i9 1 1,

Pure Oil Qompany, Chicago, v 111., a corporatino Qhio 'NO'DI'aWiHg'. AppIication MarchBI,1 948,

Serial No. 18,300

traneous fluids. Because the muds penetrateand seal many porous formations indiscriminately, that is. those which produce undesirable fluids and also those which produce the desired fluids,

the use of conventional drilling muds is not'entirely satisfactory.

Another problem which frequently occurs in the drilling of a well is that which is identified in the field as lost circulation. This is generally attributed to the penetration of a formation which contains a crack of macroscopic .dimensions' and thereby permits substantial quantities of the mud containing all its ingredients to flow thereinto. Where the problem has beenrecoge nized in the past, attempts to counteract it have .been made by incorporating fibrous materials;

such as beet pulp, oat hulls, straw, sponge rubber,

and the like into the drilling fluid with the,

thought that they would help mechanicallyito prevent this lost circulation. Also, where melon) circulation problem has been encountered, attempts have been made to use cementing agents, such as Portland cement and-gypsum of-con-.- trolled setting times .with the .theory .that :the material will vremaiirfluid long .enough to penetratethe fissure whichis .thecause of the'lost circulation-andthen will setto seal it. However, these cementing agents frequently .pass through macroscopic holes in the formation and .are lost in much the same manner asis the mud. An additional danger in the use of such cementing agentsisthat itis quite-dificult, if not impossible, to control their directionof fiow in downthe-hole operations and, consequently, it is qui te possible to seal up the bore hole itself in the attempt to seal crevices. Similar objections apply to various organic resins which have'been forced into wells to sealfissures.

Accordingly, it is a fundamental object of the instant inventionto provide a method of sealing crevices which are the cause of lost circulation in oil wellsby incorporating in a drilling fluid particles of flour dough smallenough to enter the fissures, but largeenough to be caught mediameter to a few inches 1n d1ameter and pass the mixture of discrete balls into the hole together with the mud being used, taking care to chanically therein and tough enough to have sufi cient strength to seal the formation.

The second object of the invention is to provide a method of circulating flour dough balls .into a well bore ,to induce their entry into a .flssureand, accom l sh sea in t Other. objects and advanta e 1 f th invent v .the penetration of the troublesome fissure or hole by the balls.

that small balls of .dough, which .areconip intot e o mula iqii" 91 i. the dough ballscanbe subsequently disinteg ated method r preventinglos't circulation in a well bore by sealing the fissurecausing it' with tough flour dough and involves the steps and combinations of steps having the relationship each to the other tobe hereinafter set forth. The invention also contemplates-the incorporation in a drilling mud of more or less conventional formulation of dough balls made from starch and rendered sufficiently.tough to keep their particle form, remain discrete and enter troublesome fissures in the well.

In accordance with the invention, I havefound sed preferably of about 190 parts by weight of flour, containing about 5; to 15 per cent ofgluten and parts by weightof water, .though the propor tion of fiour to' water can bewariedifrom about 2:1 to 0.5: 1, can he: kneaded to ,a sinooth consistency and boiledfor a period of 1 0 to 301mmlites totbuehe hem n ha s it h iij bery, tough form in; a drilling mud which is to be passed into a well showing a substantial amount of lost circulation. Wheat=fiou;r natu rally contains about 8 to 12 per cent of gluten and can be used directly in the productionof tou h. co ghse so fi l fiil ailm n 'fs l e 'cth i seleble.ee hqn eee he ie c e ,the l a madecy by contact thereofwith a mean acid, such'as .h dr hl riweie- In ne al f ulei qn of the. doughballs made up from parts by weight of wheatdlour wan 5c" m'20'0 parts by weightiof wa e cach .usd- Th ee e ie n ne nl fi' "t use ius sufi ei Wat 2r Wre k -Which are easily handled and then to boil these parti- 40 have the mixture fall opposite the crevice it is desired to seal. In certain instances the use of doughballs having a diameter of 3 inches may be warranted. Water can be used to carry the balls into the well. Pressure is then applied to the well byrunning in additional mud or water, for example, thereby to force the balls into the crevice. After the seal has been eifected, the surplus of dough in the bore hole is removed by breaking it up with a drill or disintegrated by means of a mineral acid, such as hydrochloric. The random size distribution of the balls used will insure The formulation of the type of dough balls to be used will be more readily understood by reference to the following examples and tabulations: Example 1.-Flour alone, and, in additional tests, flour mixed with calcium carbonate, was blended with water and the mixture kneaded until the dough became smooth and elastic. This dough was formed into balls of desired size and the balls dropped into boiling water where they were kept for a period of minutes. The boiling converted the dough balls into hard, tough, rubbery material which, for purposes of tests, were then placed in small beakers containing a small quantity of water or hydrochloric acid of various concentrations. The time required for disintegration of the dough balls was noted. The following tabulation gives results of 5 carbonate in the formulation, the more rapid will be the disintegration on contact with hydrochloric acid. For the formulation of efiective dough balls, the amount of the carbonate must be kept low enoughto permit development of a good tough dough. The disintegration of the balls including calcium carbonate is essentially a mechanical efiect resulting from the chemical action of the acid on the compound to release gas and tear the balls apart. Any material which would generate a gas upon contact with acid could be used, but alkaline earth metal carbonates are preferred because they are water insoluble, cheap the tests: and freely reactable with common acids. Various TABLE I Disintegration of dough. balls made from cake flour iigg gi gg gg Time of Disintegration in Hours Temp. F. 9 H2O GaGOs 3% 1101 13% 1101 26% E01 66.6 33.3 0 ROOm 66.6 33.3 6 166 36 22 66.6 33.3 6 150 s 6 4 50 34.4 16.6 Room 36 26 16 50 34.4 16.6 166 9 66 34.4 16.6 166 6 34. 4 31. 2 34. 4 Room 12 34.4 31.2 34.4 166 12 34.4 31.2 34.4 150 3 68.8 31.5 9.7 Room 68.8 31.6 9.7 100 68.8 31.6 9.7 150 e 44. 4 33. 4 22. 2 300m 44.4 33.4 22.2 166 44.4 33.4 I 22.2 150 After 80 hrs. ,4 disintegrated.

NOTE: (1) In all cases the size of the dough ball tested was such that the diameter was about 1% inches.

(2) In all cases it was found that the rate of disintegration of the dough balls when soaked in water was at least 5 to 10 times slower than the rate of disintegration in acid.

(3) Cake flour, used in the tests summarized. is a wheat flour containing a relatively high proportion of gluten,

i. e., about 11 per cent.

soluble gas generating materials could be used, such as the alkali metal carbonates, nitrite-amine formulations, and the like, but since the dough balls are to be carried into the well in an aqueous medium, they are not as desirableas insoluble materials because they would be leached out at least in part.

TABLE II Disintegration of dough balls made of ordinary bread flour ilg gi gg agggl Time of Disintegration in Hours Temp. F.

g fifi H20 0200. 3% E01 15% E01 26% E01 66. 6 33. 4 6. 6 Room 66 50. 6 34. 4 16. 6 Room 44 36 36 34. 4 31. 2 34. 4 Room 24 13 16 1 After hrs. )2 disintegt (1) In all cases th NOTE:

was about 1% inches. the dough balls when soaked in water was at least of disintegration in acid. (3) Bread flour, used in th flour containing about 9 per cent of gluten.

nary wheat ated.

(2) In all The distinction betweenthe problem which is to be solved by the incorporation of dough balls ,into a .well drilling fluid to seal crevices in counteracting lost circulation from the type of. sealing whichis accomplished by using various organic jell ifying materials should be noted. P-rocesses and muds employingwhat arenow conventional jellifying agents are described in such patents as United States Patents 2,259,4,1,9,.of October 14, l9.4l,-to D.'G. Hefley and J.. G. Staudt; 2,209,591, .ofJul-y 30, 1940, to C. 13. Barnes. Fundamentally, it reduces to the fact that a drilling mud. using water as the vehicle'can show an exceptionally h hloss of water in .aborehcl when itstrikes avery porousiformationin which the-pores may be microscopic in size and yet be sufiiciently open to absorb a very large quantity of the liquid. The jellifying agents described in the art are quite effective in sealing such formations where the holes are of microscopic size and the mechanical action involved is like filtration. However, where the openings to be counteracted are of macroscopic size, the organic jellifying agents are of little or no value and it is in this type of situation that the dough balls would be used. It is conceivable that both types of loss could be encountered in a single operation and treated simultaneously, for a large crack could occur in a very porous formation, thus requiring sealing of the microscopic pores and the macroscopic fissure. This could be done by incorporating the type of dough ball described in a conventional drilling mud or one containing organic jellifying material for the sealing of the microscopic pores.

liquid carrying a ent. csaidballs be nezn en r d y m xin -fion composed nhi iy 1 f ;.e tain vflour ly applying to said well sl mcient pressure to cause said dough balls to d posit. insaid fissur s. 3. The method in accordancewith clairn2in which the .dou h balls are supp ied. .ina vari y of, sizes in dispersicm in ;.a -Wel1 drill n mud.

the liquid carrying agent.

4.. The method in accordance with claim 2 in which the dough balls vary in size at random from a diameter of /8 inch to. about 3 inches.

;5. In a method in accordance-With claim2 in which the lost circulation is, counteracted, the method of reopening the well comprising, adding thereto sufficient hydrochloric acid to disintegrate the dough balls.

6. In a method of drilling a well in which lost circulation is experienced through fissures in the well formation, the method of counteracting said lost circulation which comprises carrying into said well macroscopic balls of flour dough composed chiefly of grain flour and containing 5 to 15 percent of luten with a liquid carrying agent. said balls of flour dough comprising about 0.5 to 2.0 parts of flour to 1 part of Water which have been parboiled to develop a tough, rubbery texture, and subsequently applying to said well suflicient fluid pressure to cause said dough balls to deposit in said fissures.

7. In a method of drilling a well wherein lost circulation through fissures in the well formation NOTE: In all cases the size of the dough ball tested was such that the diameter was about 1% inches.

The mud was a conventional bentonite-starch mud, typical of those used in daily drilling operations, containing bentonite, starch, barite weighting agent and defiocculating material.

Because this invention has been described with only a few examples to indicate its scope, they are to be interpreted as illustrative and not as limiting the scope thereof.

What is claimed is:

1. In a method of drilling a well in which lost circulation through fissures in the well formation is experienced, the method of counteracting said lost circulation which comprises carrying into said well difierent sized tough rubbery parboiled macroscopic balls of flour dough composed chiefly of grain flour and containing gluten with a liquid carrying agent and subsequently applying to said well suflicient fluid pressure to cause said dough balls to deposit in said fissures.

2. In a method of drilling a well in which lost circulation through fissures in the well formation is experienced, the method of counteracting said lost circulation which comprises carrying into said well macroscopic balls of flour dough with a is experienced, the steps to counteract said lost circulation which comprise carrying into said well macroscopic balls of dough with a liquid and subsequently applying to said well suflicient fluid pressure to cause said dough balls to deposit in said fissures, said dough balls comprising from about 0.5 to 2.0 parts of grain flour with sufficient water within 1 to 20 parts to develop a tough rubbery textured dough ball on parboiling and. sufficient amount of a material reactable with an acid to generate a gas but insufiicient to interfere with said dough ball formation.

8. The method in accordance with claim 7 in which 1 part of said gas forming ingredient is present in said dough balls with from 1 to 7 parts of flour.

9. The method in accordance with claim 7 in which the dough balls are supplied to the well hole in a variety of sizes in suspension in a well drilling mud as the liquid carrying agent.

10. The method in accordance with claim 7 in which the dough balls vary in size at random from a diameter of V inch to about 3 inches.

11. In a method in accordance with claim 7 in which lost eirc ulation is counteracted, the method f UNITED STATES PATENTS of reopening the well comprising, adding thereto Number Name Date sufficient hydrochloric acid to disintegrate the 1,716,925 Loomis June 11, 1929 dough 103115 by reaction With the gas forming 1 7 77 0 Ehler t 7 1930 gradient 5 1'307082 B0 to Ma 26' 1931 12. The method in accordance with claim 7 in 2:119:829 5 3 g; 1938 the gas forming ingredient is a water-in- Lehnhard, Jr. Nov. Soluble carbmate- 2,245,886 Weir et a1. June 17, 1941 13. The method 111 accordance w1th clalm '7 1n 2 337,295 Kennedy Dec. 21 1943 which the gas forming ingredient is an alkaline 1 Y 2'342 588 Larkm Feb 1944 earth metal carbonate. A H3307 7'" 4 DONALD C. BOND 2,4 L rsen Mar. 11, 19

OTHER REFERENCES REFERENCES CITED Jacobs, M. 13., The Chemistry and Technology The following references are of record in the 15 of Food. and Food Products, vol. 1, p. 629, Interfile of this patent: cience Publishers, Inc., New York, 1944. 

1. IN A METHOD OF DRILLING A WELL IN WHICH LOST CIRCULATION THROUGH FISSURES IN THE WELL FORMATION IS EXPERIENCED, THE METHOD OF COUNTERACTING SAID LOST CIRCULATION WHICH COMPRISES CARRYING INTO SAID WELL DIFFERENT SIZED TOUGH RUBBERY PARBOILED MACROSCOPIC BALLS OF FLOUR DOUGH COMPOSED CHIEFLY OF GRAIN FLOUR AND CONTAINING GLUTEN WITH A LIQUID CARRYING AGENT AND SUBSEQUENTLY APPLYING TO SAID WELL SUFFICIENT FLUID PRESSURE TO CAUSE SAID DOUGH BALLS TO DEPOSIT IN SAID FISSURES. 